1. Volume of units sold ranges from 50 to 150 and the related costs are shown below: Units Sold Salaries Commissions Rent Maintenance Utilities 50 100 150 $12,000 $12,000 $12,000 $1,250 $2,500 $3,750 $2,500 $2,500 $2,500 $1,800 $2,600 $3,400 $6,000 $12,000 $18,000 Based on the above information which of the following costs would be mixed? a. Commissions and Utilities only b. Commission, Utilities and Maintenance only C. Maintenance only d. None of the costs are mixed